Electronic devices (e.g., mobile phones, media players, electronic watches, and the like) operate when there is charge stored in their batteries. Batteries can be charged by coupling the electronic device to a power source through a physical connection, such as through a charging cord. Using charging cords to charge batteries in electronic devices, however, requires the electronic device to be physically tethered to a power outlet. Additionally, using charging cords requires the mobile device to have a receptacle configured to mate with the charging cord. The receptacle is typically a cavity in the electronic device that provides avenues within which dust and moisture can intrude and damage the device. Furthermore, a user of the electronic device has to physically connect the charging cable to the receptacle in order to charge the battery.
To avoid such shortcomings, wireless charging devices have been developed to charge electronic devices without the need for a charging cord. Electronic devices may charge by merely resting on a charging surface of the charging device. Magnetic fields generated by transmitters disposed below the charging surface may induce corresponding currents in receivers that have a corresponding inductive coil. The induced currents may be used by the electronic device to charge its internal battery.
Some conventional wireless charging applications rely upon precise alignment of transmission and receiving coils to achieve efficient wireless charging. In such devices, the efficiency of inductive charging typically drops rapidly with any misalignment of the transmission and receiving coils. This may limit the number of ways in which a charger for an electronic device can be designed and/or provide a less than ideal user experience for inductive charging.